The parasite is called Acanthamoeba. It's a single-celled organism that typically makes its way into the human eye through water and eats the cornea. This causes an infection called Acanthamoeba keratitis that can lead to blindness if left untreated.

Although anyone can develop the infection, it's most common in people who wear contact lenses, according to the Centers for Disease Control and Prevention. This happens when lenses are not properly cleaned (i.e rinsed with tap water) or wearing lenses while showering or swimming.